1. Field of the Invention
The present invention relates to the field of lighting and, in particular, to lighting systems that have a remotely located light source. Particularly, the present invention relates to high power lighting systems having remote illuminators that are capable of selectively providing dimmed and/or colored light.
2. Description of the Related Art
High energy lighting systems are often used in applications in which efficient distribution of light to a plurality of points dispersed over a relatively large area is necessary. For example, such systems are required for airport approach lighting systems (ALS) and for ship navigation lighting systems. Often, a particular application will require that light having different levels of brightness be transmitted to designated lighting points in a lighted region. Alternatively, particular regions may require different colored light. For example, to meet ICAO and FAA regulations, an approach lighting system must operate at five brightness levels depending on factors such as time of day, visibility, and other related conditions. Similar requirements exist for at least some ship navigation purposes. For example, Navy ships have particular light characteristic requirements depending on elements such as fog, etc.
Dimming of visual approach aids and navigation lighting systems, as achieved by current systems, typically is based on current or voltage monitoring, which is an indirect measurement of light attenuation. These systems are bulky and utilize high-powered electrical regulators that are expensive, sensitive to load, and subject to false indications of particular conditions associated with the circuitry caused by, for example, variations in loop current or voltage and lamp impedance, aging effects, and other factors.
More particularly, and with respect to an application of the present invention, precise requirements are set for coloring and/or dimming lights on ships depending upon certain predetermined conditions. For example, the United States Navy designates white, amber, and red light for illuminating particular areas of the ship depending upon particular conditions. In addition, similar to ALS systems regulated by the FAA, the Navy has certain light intensity requirements for its air-capable ships. Current known systems for coloring and dimming lights on ships typically consist of providing two separate systems for coloring and dimming the lights. To dim the lights, most systems utilize a rheostat for controlling voltage (and in some cases color) which renders the system bulky and not optimally cost-effective. To color the lights, known systems often utilize colored filters in conjunction with a single lamp or, in some instances, multiple lamps each corresponding to a particular color. Typically, the user must manually position an appropriate filter adjacent to the lamp such that the lamp emits light having a corresponding color. The user manually places a piece of colored plexiglass adjacent to all of the lamps (potentially hundreds) for each light on the ship that requires a particular color. This is a tedious and inefficient task requiring an unreasonable amount of man-hours to maintain.
Some known high-energy lighting systems that provide dimmed light allow the user to select a particular brightness by setting the regulated constant current supplied to the light sources. Control and monitoring of the current is typically provided by an electronic subsystem. Notably, there are a variety of attendant problems with systems that measure and regulate only electrical parameters while maintaining a constant output current. For example, variations in the brightness of the lamps across the lighted area can be caused by dispersion parameters of individual incandescent lamps, aging, different resistances in current loops, etc.; further, such variations often occur even with perfect monitoring of the output current. Overall, known systems provide imperfect control and monitoring of the supplied light whether or not the light is dimmed or colored.
Further, one of the major problems encountered with a system having a plurality of light sources is light source failure. Replacing the lamps in such a system is a significant maintenance expense.
One solution to at least some of these problems is proposed in U.S. Pat. No. 5,629,996, which discloses a high definition universal remote lighting system (RLS) for an approach lighting system (ALS) that combines 1) a single light source coupled to a light pipe (or a bundle of light pipes) such as a fiber optic cable, and 2) a beamformer coupled to each light pipe for shaping the light according to particular requirements. This system separates the light source from the lighting points to provide high energy lighting to a remote location, and can illuminate several lighting points with a single light source. The system includes a direct optical monitoring loop through the use of a liquid crystal optical switch device (OSD) in conjunction with currently-used multilevel current regulators to provide fine light control and an absolute indication of the state of each ALS light source. The beamformers operate to finely shape the light and can dim/color the light as necessary. Although they are effective at meeting precise lighting requirements, beamformers are comprised of a relatively complex arrangement of components (light transformers, holographic diffusers, etc.) that add to system cost. Therefore, a conspicuously absent feature of known remote illumination systems is a way to dim and/or color the light output by the light source, prior to coupling the light to the distribution light pipes, with an apparatus that is relatively inexpensive to manufacture and yet provides a highly reliable output. Another feature absent from known systems is a ready way to control the light supplied to the individual lighting points corresponding to particular areas.
The field of high energy lighting systems is in need of an illuminator for dimming/coloring the source light, preferably at the light source, in a cost-effective fashion. Also, a system that combines the benefits associated with remote source lighting, including using a single light source to provide light at a variety of points at a remote location, with such an illuminator, is desired. In addition, the lighting system should be controllable from a plurality of remote locations for convenient modification of the characteristics of the light supplied to particular regions of a lighted area.